Display device with a built-in touch panel

ABSTRACT

A display device with a built-in touch panel includes a first substrate, a second substrate, plural pixel electrodes provided between the first substrate and the second substrate, plural common electrodes provided between the first substrate and the second substrate, and plural detection electrodes provided on the first substrate. An image is displayed by light control using an electric field generated between the plural pixel electrodes and the plural common electrodes. The presence or absence of touch is detected by a difference in capacitance due to the presence or absence of a material interrupting the electric field generated between one of the detection electrodes and one of the common electrodes. Each of the detection electrodes includes a through hole.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese applicationJP2013-51958 filed on Mar. 14, 2013, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device with a built-in touchpanel.

2. Description of the Related Art

In recent years, with the spread of mobile devices, a touch paneltechnique to support a human-friendly graphical user interface becomesimportant. As this touch panel technique, an electrostatic capacitivecoupling type touch panel is known. In a general electrostaticcapacitive coupling type touch panel, a touch panel substrate isprovided in which a conductive coating (transparent conductive film) isapplied to a surface of a glass substrate, and when a finger toucheshere, position detection is performed. A liquid crystal display panelwith a touch panel is also known in which this touch panel substrate isattached to a surface of a liquid crystal display panel, and when afinger touches a menu screen displayed on the liquid crystal displaypanel, an operation corresponding to the menu is performed (JP2006-146895 A).

In a display panel with a touch panel, in general, a touch panel isoverlapped on a display region of the display panel to display imagesand character information and is used. In the related art display panelwith the touch panel, the touch panel and the display panel areseparately produced, and are overlapped and combined to form the finalproduct. Thus, in the related art display panel with the touch panel,since the separately produced touch panel and display panel must beoverlapped, there is a problem that the display panel with the touchpanel becomes thick.

SUMMARY OF THE INVENTION

An object of the invention is to provide a display device with abuilt-in touch panel which can be made thinner than the related art byhaving the built-in touch panel.

(1) According to an aspect of the invention, a display device with abuilt-in touch panel includes a first substrate, a second substrate,plural pixel electrodes provided between the first substrate and thesecond substrate, plural common electrodes provided between the firstsubstrate and the second substrate, and plural detection electrodesprovided on the first substrate, an image is displayed by light controlusing an electric field generated between the plural pixel electrodesand the plural common electrodes, presence or absence of a touch isdetected by a difference in capacitance due to presence or absence of amaterial interrupting the electric field generated between one of thedetection electrodes and one of the common electrodes, and each of thedetection electrodes includes a through hole. According to thisinvention, since the touch panel is built in, the display device isthinner than the related art display device with the touch panel.Besides, since the detection electrode includes the though hole, edgesincrease. Thus, an electric field generated in an opposing regionbetween the detection electrode and the common electrode decreases, anda fringe electric field coming around from the outside of bothincreases. The fringe electric field is used to detect the presence orabsence of the touch. Accordingly, since the fringe electric fieldincreases, the detection sensitivity can be improved.

(2) In the display device with the built-in touch panel as recited in(1), it is preferable that a land part in an electrically floating stateis provided inside the through hole.

(3) In the display device with the built-in touch panel as recited in(1) or (2), it is preferable that the plural detection electrodes arearranged with intervals between the adjacent detection electrodes, adummy electrode in an electrically floating state is provided betweenthe adjacent detection electrodes, and the dummy electrode includes adummy through hole.

(4) In the display device with the built-in touch panel as recited in(3), it is preferable that a dummy land part in an electrically floatingstate is provided inside the dummy through hole.

(5) In the display device with the built-in touch panel as recited inany one of (1) to (4), it is preferable that the plural commonelectrodes extend in a lateral direction, the adjacent common electrodesare arranged side by side in a longitudinal direction, the pluraldetection electrodes extend in the longitudinal direction and theadjacent detection electrodes are arranged side by side in the lateraldirection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a display device with a built-in touchpanel according to an embodiment of the invention.

FIG. 2 is a decomposed perspective view of a main part of the displaydevice with the built-in touch panel according to the embodiment of theinvention.

FIG. 3 is a view showing a circuit for displaying an image on a displaypanel.

FIG. 4 is a plan view showing details of a detection electrode.

FIG. 5 is a view showing an electric field generated between thedetection electrode and a common electrode.

FIG. 6 is a view for explaining an operation to detect the presence orabsence of touch.

FIG. 7 is a view for comparing the embodiment with the prior art withrespect to change in capacitance due to the presence or absence oftouch.

FIG. 8 is a view showing modified example 1 of the embodiment.

FIG. 9 is a view showing modified example 2 of the embodiment.

FIG. 10 is a view showing modified example 3 of the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a sectional view of a display device with a built-in touchpanel according to an embodiment of the invention. FIG. 2 is adecomposed perspective view of a main part of the display device withthe built-in touch panel according to the embodiment of the invention.Although the following description relates to an example in which theinvention is applied to a liquid crystal display device, the inventioncan be applied also to a display device other than the liquid crystaldisplay device (for example, an EL (Electro Luminescence) displaydevice).

The display device with the built-in touch panel includes a firstsubstrate 10 and a second substrate 12. A liquid crystal material 14 isdisposed between the first substrate 10 and the second substrate 12.Orientation films 16 are respectively formed between the first substrate10 and the second substrate 12 and at positions where they sandwich theliquid crystal material 14.

The first substrate 10 is made of a translucent material (for example,glass). The first substrate 10 is a color filter substrate, and anot-shown colored layer and a black matrix are formed. The orientationfilm 16 is formed on the first substrate 10. The orientation film 16 isformed on the not-shown colored layer and the black matrix.

The second substrate 12 is made of a translucent material (for example,glass). The second substrate 12 is called also a TFT substrate since athin film transistor 18 is formed. The thin film transistor 18 includesa semiconductor film 20 of polysilicon or the like, a gate insulatingfilm 22 covering the semiconductor film 20, a gate electrode 24 disposedabove the semiconductor film 20 through the gate insulating film 22, anda source electrode 26 and a drain electrode 28 which pass through thegate insulating film 22 and are electrically connected to thesemiconductor film 20.

One of the source electrode 26 and the drain electrode 28 iselectrically connected to a pixel electrode 30. A common electrode 34 isformed at a layer position different from the pixel electrode 30 throughan insulating film 32. In the example of FIG. 1, although the pixelelectrode 30 is positioned above the common electrode (on the sidedistant from the second substrate 12), they may be disposed upside down.

A liquid crystal display panel 36 is constructed of the above parts. Animage is displayed by light control using an electric filed generatedbetween the plural pixel electrodes 30 and the plural common electrodes34. In this embodiment, the liquid crystal material 14 is driven by theelectric field generated between the pixel electrodes 30 and the commonelectrodes 34. Since the pixel electrodes 30 and the common electrodes34 are formed on the second substrate 12, the electric field generatedbetween the pixel electrodes 30 and the common electrodes 34 is alateral electric field. Alternatively, the pixel electrodes 30 areformed on the second substrate 12, the common electrodes 34 are formedon the first substrate 10, and the liquid crystal material 14 may bedriven by a longitudinal electric filed. In either of the structures,the pixel electrodes 30 and the common electrodes 34 are disposedbetween the first substrate 10 and the second substrate 12.

The display device with the built-in touch panel includes detectionelectrodes 38 formed on the first substrate 10. In the example of FIG.1, the detection electrodes 38 are disposed on a surface of the firstsubstrate 10 on the opposite side to the liquid crystal material 14. Asshown in FIG. 2, the plural common electrodes 34 extend in the lateraldirection and the adjacent common electrodes are arranged side by sidein the longitudinal direction.

The presence or absence of touch is detected by a difference incapacitance due to the presence or absence of a material interruptingthe electric field generated between the detection electrodes 38 and thecommon electrodes 34. Particularly, different voltages are respectivelyapplied to the detection electrode 38 and the common electrode 34 toform the electric field (fringe electric filed) between both theelectrodes (particularly, outside the opposing region). The presence orabsence of the touch is detected by the difference in the capacitancedue to the presence or absence of the material (for example, a finger40) interrupting the electric field generated between the detectionelectrode 38 and the common electrode 34. That is, a touch panel 42 isconstructed of the first substrate 10, the detection electrodes 38 andthe common electrodes 34. The touch panel 42 is bonded with a frontpanel 46 through an adhesive layer 44 and is reinforced.

According to this embodiment, since the touch panel 42 is built in, thedevice can be made thinner than the prior art. Besides, since the liquidcrystal display panel 36 and the touch panel 42 share the firstsubstrate 10, a countermeasure against superimposing displacement ofboth is not required.

The first substrate 10 has a rectangular planar shape, and the pluraldetection electrodes 38 extend in the longitudinal direction along thelong side. A flexible wiring substrate 48 for electrical connectionbetween the detection electrodes 38 and the outside is attached to thefirst substrate 10. An integrated circuit chip 50 having a built-indriving circuit of liquid crystal is mounted on the second substrate 12,and a flexible wiring substrate 52 for electrical connection to theoutside is attached.

FIG. 3 is a view showing a circuit for displaying an image on the liquidcrystal display panel 36. The pixel electrodes 30 are formed in an imagedisplay region 56. Since pixels are formed of the plural pixelelectrodes 30, the region surrounding the plural pixel electrodes 30 isthe image display region 56. The common electrodes 34 are formed in theimage display region 56. The common electrodes 34 are set to a referencepotential (for example, GND), and a voltage corresponding to thebrightness of the pixel is applied to the pixel electrode 30. An imageis displayed by light control (for example, driving of the liquidcrystal material 14) using the electric field generated between thepixel electrodes 30 and the common electrodes 34.

The common electrodes 34 are electrically connected to a common wiring58, and the pixel electrodes 30 are electrically connected to a signalline 60. A switching element 62 (for example, the thin film transistor18 shown in FIG. 1) is connected between the pixel electrode 30 and thesignal line 60, and electrical conduction and interruption between thepixel electrode 30 and the signal line 60 can be performed. Theswitching element 62 is connected to a scanning line 64 drawn out from anot-shown scanning circuit, and is driven (on/off) by a scanning signalinputted to the scanning line 64.

FIG. 4 is a plan view showing the details of the detection electrodes38. The plural detection electrodes 38 extend in the longitudinaldirection and the adjacent detection electrodes are arranged side byside in the lateral direction. Incidentally, the plural commonelectrodes 34 indicated by broken lines extend in the lateral directionand the adjacent common electrodes are arranged side by side in thelongitudinal direction. The plural detection electrodes 38 are arrangedwith intervals between the adjacent detection electrodes. The intervalis provided so that the fringe electric filed can be increased. Thedetection electrode 38 includes through holes 38 a. The detectionelectrode 38 is made of a conductive material having a hightransmittance to visible light, for example, ITO (Indium Tin Oxide).However, when the film thickness becomes thick, the detection electrodeis easily visually recognized from the outside. Then, the through holes38 a are formed in the detection electrode 38, so that the detectionelectrode 38 is hard to be visually recognized and the image is easilyvisually seen.

Dummy electrodes 54 are disposed between the adjacent detectionelectrodes 38. A gap is provided between the detection electrode 38 andthe dummy electrode 54. In the example of FIG. 4, the plural dummyelectrodes 54 are arranged side by side with intervals in the intervaldirection between the adjacent detection electrodes 38. Besides, theplural dummy electrodes 54 are also arranged side by side with intervalsin the direction (longitudinal direction) in which the detectionelectrodes 38 extend. The dummy electrode 54 is made of the samematerial as the detection electrode 38. The detection electrodes 38 canbe made hard to be visually recognized also by disposing the dummyelectrodes 54 between the detection electrodes 38, and the image can bemade easily visually seen by this.

The dummy electrodes 54 are in an electrically floating state. That is,the dummy electrodes 54 are not connected to a reference potential suchas GND, and are not connected to the detection electrodes 38 and otherwiring. However, when necessary, the dummy electrodes 54 may beconnected to the reference potential such as GND. The plural dummyelectrodes 54 are arranged with intervals between the adjacent dummyelectrodes. The dummy electrode 54 includes dummy through holes 54 a.When the dummy electrodes 54 are disposed, a region where the conductordoes not exist becomes narrow, and the fringe electric field decreases.However, since the dummy through holes 54 a are formed, the amount ofdecrease of the fringe electric field is small. Besides, the dummythrough holes 54 a are formed, so that the dummy electrodes 44 are hardto be visually recognized, and the image is easily visually seen.

FIG. 5 is a view showing the electric field generated between thedetection electrodes 38 and the common electrodes 34. The electric field(normal electric field) is generated as indicated by electric lines offorce in the opposing region between the detection electrode 38 and thecommon electrode 34 (between the opposing surfaces). Besides, the fringeelectric field as indicated by electric lines of force is generated in aregion except for the opposing region between the detection electrode 38and the common electrode 34. The fringe electric field is mainlydistributed between the edge of the detection electrode 38 and thecommon electrode 34. Since the detection electrode 38 includes thethrough holes 38 a, the number of edges increase. Thus, the normalelectric field generated in the opposing region between the detectionelectrode 38 and the common electrode 34 decreases, and the fringeelectric field coming around from the outside of both increases.

FIG. 6 is a view for explaining the operation of detecting the presenceor absence of touch. The fringe electric field is used to detect thepresence or absence of the touch. For example, when the finger touches,the finger 40 becomes GND and interrupts the fringe electric field.Since the capacitance formed between the detection electrode 38 and thecommon electrode 34 is decreased by this, the presence or absence of thetouch can be detected by detecting the decrease (capacitancedifference).

In this embodiment, as described above, since the through holes 38 a areformed in the detection electrode 38, the fringe electric fieldincreases. When a touch is performed, since the increased fringeelectric field is interrupted, the capacitance is significantlydecreased. Accordingly, the detection sensitivity of the touch can beimproved.

FIG. 7 is a view for comparing this embodiment with the prior art withrespect to the change in capacitance due to the presence or absence oftouch. A touch occurs during a period of T1 to T2, and a change incapacitance is shown in the graph. As compared with the prior art, it isunderstood that in this embodiment, the change in capacitance(capacitance difference) due to the presence or absence of the touch islarge. In this embodiment, for example, the circuit is designed suchthat it is determined that the touch occurs when the capacitance isdetected to become smaller than C1, and it is determined that there isno touch when the capacitance is detected to become larger than C2. Anerroneous operation is prevented by providing the difference between C1and C2, and as the difference increases, the erroneous operation becomeshard to be performed. In this embodiment, since the change incapacitance (capacitance difference) due to the presence or absence ofthe touch is large, the difference between C1 and C2 can be increased.By this, the erroneous operation of erroneously recognizing the presenceor absence of the touch can be prevented.

FIG. 8 is a view showing modified example 1 of the embodiment. In thisexample, a detection electrode 138 includes a land part 166 in anelectrically floating state inside a through hole 138 a. The throughhole 138 a can be made hard to be visually recognized by providing theland part 166, and an image can be made easily visually seen by this.

FIG. 9 is a view showing modified example 2 of the embodiment. In thisexample, a dummy electrode 254 includes a dummy land part 266 in anelectrically floating state inside a dummy through hole 254 a. The dummythrough hole 254 a can be made hard to be visually recognized byproviding the dummy land part 266, and an image can be made easilyvisually seen by this.

FIG. 10 is a view showing modified example 3 of the embodiment. In thisexample, the dummy electrode is eliminated, and an interval betweenadjacent detection electrodes 338 is narrowed. Since the intervalbetween the detection electrodes 338 is narrowed, the width of thedetection electrode 338 can be increased, and the resistance can bedecreased. Besides, since the interval is narrow, the detectionelectrode 338 is hard to be visually recognized, and an image is easilyvisually seen by this. Incidentally, when the interval between theadjacent detection electrodes 338 is narrowed, a region through whichelectric lines of force pass becomes narrow, and the fringe electricfield passing through between the adjacent detection electrodes 338 isweakened. However, the fringe electric field is increased by formingthrough holes 338 a.

While there have been described what are at present considered to becertain embodiments of the invention, it will be understood that variousmodifications may be made thereto, and it is intended that the appendedclaims cover all such modifications as fall within the true spirit andscope of the invention.

What is claimed is:
 1. A display device with a built-in touch panel,comprising: a first substrate; a second substrate; a plurality of pixelelectrodes provided between the first substrate and the secondsubstrate; a plurality of common electrodes provided between the firstsubstrate and the second substrate; and a plurality of detectionelectrodes provided on the first substrate, wherein an image isdisplayed by light control using an electric field generated between theplurality of pixel electrodes and the plurality of common electrodes,presence or absence of a touch is detected by a difference incapacitance due to presence or absence of a material interrupting theelectric field generated between one of the detection electrodes and oneof the common electrodes, and each of the detection electrodes includesa through hole.
 2. The display device with the built-in touch panelaccording to claim 1, wherein a land part in an electrically floatingstate is provided inside the through hole.
 3. The display device withthe built-in touch panel according to claim 1, wherein the plurality ofdetection electrodes are arranged with intervals between the adjacentdetection electrodes, a dummy electrode in an electrically floatingstate is provided between the adjacent detection electrodes, and thedummy electrode includes a dummy through hole.
 4. The display devicewith the built-in touch panel according to claim 3, wherein a dummy landpart in an electrically floating state is provided inside the dummythrough hole.
 5. The display device with the built-in touch panelaccording to claim 1, wherein the plurality of common electrodes extendin a lateral direction and the adjacent common electrodes are arrangedside by side in a longitudinal direction, and the plurality of detectionelectrodes extend in the longitudinal direction and the adjacentdetection electrodes are arranged side by side in the lateral direction.